Animals use chemical cues from the environment to seek out high quality food sources, while at the same time avoiding poisonous compounds. Despite the importance of the gustatory system, little is known about the basic principles of taste reception. The goal of this project is to elucidate basic principles of taste system function and organization. The experimental plan takes advantage of the fruit fly Drosophila as a model system for the study of taste. Drosophila has relatively simple taste organs, containing several hundred receptor neurons. A number of powerful molecular genetic tools can be utilized in Drosophila, and Drosophila taste neurons can be examined electrophysiologically, enabling us to examine electrical impulses in individual taste hairs to a particular stimulus, the first aim is to provide a functional map of the labellum, the primary Drosophila taste organ, using a diverse panel of taste compounds. This analysis should determine the number of functionally distinguishable taste sensilla. The second aim is to identify ligands for selected gustatory receptor genes. This aim is designed to address the tuning breadth of taste receptors, a critical issue in taste coding.